Chemical Changes:
* Mass is conserved. This is a fundamental principle in chemistry known as the Law of Conservation of Mass. During a chemical reaction, the atoms themselves are rearranged, but they are not created or destroyed. This means the total mass of the reactants (starting materials) must equal the total mass of the products (the substances formed).
* Examples: Burning wood (wood + oxygen -> ash + carbon dioxide + water), rusting of iron (iron + oxygen -> iron oxide), baking a cake (flour + eggs + sugar + butter -> cake).
Physical Changes:
* Mass is also conserved. Physical changes alter the appearance or state of matter, but they do not involve changes in the chemical composition of the substance.
* Examples: Melting ice (solid water -> liquid water), boiling water (liquid water -> gaseous water), cutting paper (a piece of paper is divided into smaller pieces), dissolving sugar in water (sugar molecules are dispersed in water but still exist as sugar).
Key Takeaway: Whether it's a chemical or a physical change, the total mass of a closed system will remain constant. This is because matter cannot be created or destroyed, only transformed from one form to another.
